US6274273B1 - Positive active material for rechargeable lithium battery and method of preparing same - Google Patents

Positive active material for rechargeable lithium battery and method of preparing same Download PDF

Info

Publication number
US6274273B1
US6274273B1 US09/669,775 US66977500A US6274273B1 US 6274273 B1 US6274273 B1 US 6274273B1 US 66977500 A US66977500 A US 66977500A US 6274273 B1 US6274273 B1 US 6274273B1
Authority
US
United States
Prior art keywords
active material
cobalt
positive active
limn
heat
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US09/669,775
Inventor
Jae-phil Cho
Geun-bae Kim
Yong-Chul Park
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Samsung SDI Co Ltd
Original Assignee
Samsung SDI Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Samsung SDI Co Ltd filed Critical Samsung SDI Co Ltd
Assigned to SAMSUNG SDI CO., LTD. reassignment SAMSUNG SDI CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: CHO, JAE-PHIL, KIM, GEUN-BAE, PARK, YONG-CHUL
Application granted granted Critical
Publication of US6274273B1 publication Critical patent/US6274273B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G45/00—Compounds of manganese
    • C01G45/12—Manganates manganites or permanganates
    • C01G45/1221—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof
    • C01G45/1242—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof of the type [Mn2O4]-, e.g. LiMn2O4, Li[MxMn2-x]O4
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G51/00—Compounds of cobalt
    • C01G51/40—Cobaltates
    • C01G51/42—Cobaltates containing alkali metals, e.g. LiCoO2
    • C01G51/44—Cobaltates containing alkali metals, e.g. LiCoO2 containing manganese
    • C01G51/54—Cobaltates containing alkali metals, e.g. LiCoO2 containing manganese of the type [Mn2O4]-, e.g. Li(CoxMn2-x)04, Li(MyCoxMn2-x-y)O4
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/30—Three-dimensional structures
    • C01P2002/32—Three-dimensional structures spinel-type (AB2O4)
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/50—Solid solutions
    • C01P2002/52—Solid solutions containing elements as dopants
    • C01P2002/54—Solid solutions containing elements as dopants one element only
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a positive active material for a rechargeable lithium battery and a method of preparing the same, and more particularly, to a positive active material for a rechargeable lithium battery exhibiting good cycle life characteristics at high temperatures.
  • Manganese-based active materials such as LiMn 2 O 4 , and LiMnO 2 , among all of the positive active materials, are the easiest to prepare, are less expensive than the other materials and have environmentally friendly characteristics.
  • LiMn 2 O 4 is particularly stable for battery use and is thus attractive for electric vehicle applications.
  • LiMn 2 O 4 exhibits good room-temperature cycle life characteristics, but poor high-temperature cycle life characteristics.
  • the manganese in LiMn 2 O 4 has an atomic value of 3.5, and thus it substantially has a formal charge of +3 and a formal charge of +4. Therefore, two types of Mn in LiMn 2 O 4 exist: Mn 3+ and Mn 4+ .
  • Mn 3+ When the ambient temperature is raised, stable Mn 4+ is not oxidized or reduced, but unstable Mn 3+ is oxidized to Mn 4+ or reduced to Mn 2+ . This is a disproportionate reaction and causes an abrupt loss of capacity at high temperatures. This capacity loss mostly occurs in initial charge-discharge cycles, for example, between the first and tenth charge-discharge cycles.
  • the positive active material for a rechargeable lithium battery Li 1+x Mn 2 ⁇ y Co y O 4 wherein ⁇ 01 ⁇ x ⁇ 0.1 and 0 ⁇ y ⁇ 0.1.
  • the positive active material has a concentration of Co at a surface portion higher than that in a central portion.
  • the surface portion is defined as a region from the outermost surface to a depth of 10 microns.
  • the present invention further provides a method of preparing the positive active material for a rechargeable lithium battery.
  • lithium salts, cobalt salts, alcohols and chelating agents are mixed, and the mixture is heated to obtain a sol or gel type cobalt material.
  • the sol or gel type cobalt material is then mixed with LiMn 2 O 4 and the resulting mixture is heat-treated.
  • FIGS. 2 a and 2 b are scanning electron microscopy (SEM) photographs illustrating a material heat-treated at a low temperature in Example 1 of the present invention
  • FIGS. 3 a and 3 b are SEM photographs illustrating a positive active material heat-treated at low and high temperatures according to Example 1 of the present invention
  • FIGS. 4 a and 4 b are SEM photographs illustrating a positive active material according to Comparative example 1;
  • FIG. 5 a is a graph illustrating an electron probe microanalysis (EPMA) result of a positive active material according to Example 1 of the present invention
  • FIG. 5 b is a SEM photograph of the positive active material sample used in the EPMA
  • FIG. 7 is a graph illustrating initial charge and discharge characteristics of the positive active materials according to Example 1 and Comparative Example 1.
  • Cobalt salts and lithium salts are weighed in the desired ratio, the salts and a chelating agent are mixed with an alcohol, and the mixture is heated to prepare a sol or a gel type cobalt material.
  • the cobalt salt may be cobalt hydroxide, cobalt nitrate or cobalt carbonate, and the lithium salt may be lithium carbonate, lithium nitrate or lithium hydroxide.
  • the chelating agent may be oxalic acid, citric acid or glycine, and the alcohol may be ethanol or methanol.
  • the cobalt salts, lithium salts and alcohols are not limited to the above compounds.
  • LiMn 2 O 4 having a spinel phase.
  • LiMn 2 O 4 may be produced by mixing manganese salts with lithium salts in the desired ratio and sintering the mixture at a temperature ranging from about 750 to 800° C.
  • LiMn 2 O 4 may be commercially purchased.
  • the manganese salts may be manganese acetate or manganese dioxide, and the lithium salts may be lithium carbonate, lithium nitrate or lithium hydroxide.
  • the manganese salts and lithium salts are not limited to the above compounds.
  • the mixture of the cobalt material and manganese compound is heat-treated at a temperature ranging from 550 to 850° C.
  • the heat-treatment temperature preferably ranges from 700 to 850° C. because the crystallinity of LiCoO 2 is increased.
  • a pre-heat-treatment step may be performed at a temperature ranging from 100 to 300° C.
  • LiCoO 2 reacts with LiMn 2 O 4 to generate Li 1+x Mn 2 ⁇ y Co y O 4 wherein 0.1 ⁇ x ⁇ 0.1 and 0 ⁇ y ⁇ 0.1.
  • the reaction occurs more actively in the surface portion than in the central portion, and thus the Co content in the surface portion of LiMn 2 O 4 is higher than in the central portion thereof.
  • the surface portion refers to a region from an outermost surface to a depth of 10 microns.
  • the ratio of the concentration of Co in the central portion to that in the surface portion ranges from 1:1.05 to 1:1.3.
  • Electrolytes of rechargeable lithium batteries are generally non-aqueous, but a trace of water may be present in the electrolytes. Water reacts with lithium salts such as LiPF 6 in the electrolyte to generate strong acids such as HF. The generated HF attacks Mn present at the surface of the manganese-based positive active material, and Mn is eluted into the electrolyte such that the active material disintegrates. As a result, the cycle life characteristics, particularly the high-temperature cycle life characteristics, are extremely deteriorated. In the present invention, Co, which is abundant in the surface of LiMn 2 O 4 , protects Mn against attack by HF.
  • the positive active material is used in rechargeable lithium batteries.
  • a negative electrode is produced with a carbonaceous active material such as graphite or carbon, from or into which lithium ions are deintercalated or intercalated.
  • a non-aqueous liquid electrolyte or a polymer electrolyte may be used.
  • separators polymer films known in the related arts may be used.
  • Lithium acetate and cobalt acetate in the molar ratio of 1:2 were added to 50 ml of methanol, and the mixture was uniformly shaken using a magnetic bar. 2 g of citric acid were then added to the mixture, and the resulting mixture was heated at 50° C. until a sticky gel was obtained. LiMn 2 O 4 powder was added to the gel and uniformly mixed. Thereafter, the mixture obtained was pre-heat-treated at 150° C. for 3 hours, and the pre-heat-treated material was again heat-treated at 800° C. for 12 hours to produce a positive active material for a rechargeable lithium battery.
  • Li 2 CO 3 was uniformly mixed with MnO 2 and the mixture was sintered at 790° C. for 24 hours. The sintered material was cooled to room temperature to produce LiMn 2 O 4 .
  • Li 2 CO 3 , MnO 2 and Co(OH) 2 were mixed, and the mixture was sintered at 790° C. for 24 hours to produce Li 1.03 Mn 1.97 CO 0.03 O 4 .
  • the XRD of the material pre-heat-treated at 150° C. and the positive active material heat-treated at 800° C. according to Example 1 were measured, and the results are shown in FIG. 1 .
  • the XRD result of the positive active material according to Comparative Example 1 is also shown in FIG. 1 .
  • the material pre-heat-treated at 150° C. (B in FIG. 1) and the positive active material heat-treated at 800° C. for 12 hours (C in FIG. 1) exhibit no LiCoO 2 phase, like the positive active material according to Comparative Example 1 (A in FIG. 1 ).
  • the results indicate that a very thin layer of LiCoO 2 is coated on LiMn 2 O 4 .
  • FIGS. 2 a and b SEM photographs of the pre-heat-treated material and the heat-treated active material according to Example 1 are presented in FIGS. 2 a and b, and FIGS. 3 a and b respectively.
  • FIGS. 4 a and b show the SEM photographs of the active material according to Comparative Example 1.
  • FIGS. 2 b, 3 b and 4 b are the SEM photographs of FIGS. 2 a, 3 a, and 4 a, respectively, enlarged 10 times.
  • the surface of the material heat-treated at 150° C. (FIGS. 2 a and b ) is different from that of LiMn 2 O 4 (FIGS. 4 a and b ). Whereas, the surface of the positive active material which was again heat-treated at 800° C.
  • the material heat-treated at the low temperature has the LiCoO 2 coating layer such that it has a smooth surface, which is different from that of LiMn 2 O 4 , but the material heat-treated again has no LiCoO 2 coating layer or octahedral type spinel, similar to LiMn 2 O 4 .
  • the results show that LiCoO 2 reacts with LiMn 2 O 4 at high temperatures to generate Li 1+x Mn 2 ⁇ y Co y O 4 .
  • elemental analysis results show that the powder heat-treated at 800° C. was Li 1.03 Mn 1.97 Co 0.03 O 4 .
  • FIG. 5 a shows a SEM photograph of the positive active material sample used in the EPMA.
  • the Co content in the active material according to Example 1 is highest at the outermost surface portion and is higher than the central portion from the outermost surface to a depth of 10 microns.
  • FIG. 6 shows the high-temperature (55° C.) cycle life characteristics of the half-cell using the positive active material according to Example 1, Comparative Example 1 and Comparative Example 2 (Synthesized Li 1.03 Mn 1.97 Co 0.03 O 4 ).
  • metallic lithium was used as the reference electrode
  • polyvinylidene fluoride was used as the binder
  • Carbon black was used as the conductive agent
  • N-methyl pyrrolidone was used as the solvent.
  • the separator was obtained from Celgard Co., and the electrolyte used was LiPF 6 in ethylene carbonate and dimethyl carbonate.
  • the active material according to Example 1 exhibited excellent high-temperature cycle life characteristics.
  • FIG. 7 shows the initial charge and discharge capacity of the half-cells.
  • the cell according to Example 1 exhibited a smaller irreversible capacity than that of Comparative Example 1.
  • the positive active material of the present invention has a surface coated with LiCoO 2, which stops the elution of Mn, so the positive active material has cycle life characteristics that are improved by at least 20%, compared with LiMn 2 O 4 .

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)
  • Secondary Cells (AREA)

Abstract

Disclosed is a positive active material for a rechargeable lithium battery having a higher concentration of Co in the surface portion than in the central portion. The surface portion is a region from the outermost surface to a depth of 10 microns. The positive active material is represented Li1+xMn2−yCoyO4 wherein −0.1<x0.1 and 0<y<0.1. The positive active material is produced by obtaining a sol or gel cobalt material by mixing lithium salts, cobalt salts, an alcohol and chelating agents and heating the mixture, mixing the sol or gel cobalt material with LiMn2O4, and heat-treating the resulting mixture.

Description

CROSS REFERENCE TO RELATED APPLICATION
This application claims priority to Korean patent application No. 1999-51149 filed on Nov. 17, 1999, the content of which is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to a positive active material for a rechargeable lithium battery and a method of preparing the same, and more particularly, to a positive active material for a rechargeable lithium battery exhibiting good cycle life characteristics at high temperatures.
BACKGROUND OF THE INVENTION
In recent years, the development of miniaturized portable electronics has provided a need for a rechargeable lithium battery having a high capacity as well as a light weight. The capacity of the rechargeable lithium battery depends on the positive active materials. The electrochemical characteristics of the positive active materials influence the high-rate cycle characteristics and the capacity retention of the rechargeable lithium battery.
Manganese-based active materials such as LiMn2O4, and LiMnO2, among all of the positive active materials, are the easiest to prepare, are less expensive than the other materials and have environmentally friendly characteristics. Among such manganese-based compounds, LiMn2O4 is particularly stable for battery use and is thus attractive for electric vehicle applications.
LiMn2O4 exhibits good room-temperature cycle life characteristics, but poor high-temperature cycle life characteristics. The manganese in LiMn2O4 has an atomic value of 3.5, and thus it substantially has a formal charge of +3 and a formal charge of +4. Therefore, two types of Mn in LiMn2O4 exist: Mn3+ and Mn4+. When the ambient temperature is raised, stable Mn4+ is not oxidized or reduced, but unstable Mn3+ is oxidized to Mn4+ or reduced to Mn2+. This is a disproportionate reaction and causes an abrupt loss of capacity at high temperatures. This capacity loss mostly occurs in initial charge-discharge cycles, for example, between the first and tenth charge-discharge cycles.
In addition, when a battery using a manganese-based material such as LiMn2O4 is charged and discharged many times, particularly at high temperatures, a side reaction between the electrolyte and the manganese-based material occurs at the surface of the manganese-based material. It is believed that H2O reacts with LiPF6 in the electrolyte to generate the strong acid HF, which attacks Mn presented at the surface of the manganese-based active material, and the attacked Mn is eluted into and dissolved in the electrolyte, so the active material disintegrates. This side reaction seriously deteriorates the cycle life characteristics of the battery.
Attempts to solve these problems have been performed by synthesizing a material including at least one equivalent of Li, or partially substituting oxygen (O) with fluoride (F) in a spinel manganese-based material. However, those methods do not effectively improve the cycle life characteristics of the battery, particularly at high temperatures.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a positive active material for a rechargeable lithium battery exhibiting good high-temperature cycle life characteristics.
It is another object to provide a method of preparing the positive active material for a rechargeable lithium battery.
These and other objects may be achieved by the positive active material for a rechargeable lithium battery Li1+xMn2−yCoyO4 wherein −01<x<0.1 and 0<y<0.1. The positive active material has a concentration of Co at a surface portion higher than that in a central portion. The surface portion is defined as a region from the outermost surface to a depth of 10 microns.
In order to achieve these objects and others, the present invention further provides a method of preparing the positive active material for a rechargeable lithium battery. In this method, lithium salts, cobalt salts, alcohols and chelating agents are mixed, and the mixture is heated to obtain a sol or gel type cobalt material. The sol or gel type cobalt material is then mixed with LiMn2O4 and the resulting mixture is heat-treated.
BRIEF DESCRIPTION OF THE DRAWINGS
The file of this patent contains at least one drawing executed in color. Copies of this patent with color drawing(s) will be provided by the Patent and Trademark Office upon request and payment of the necessary fee.
A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying figures, wherein:
FIG. 1 is a graph illustrating X-ray diffraction (XRD) results of a material heat-treated at a low temperature according to Example 1, a positive active material heat-treated at low and high temperatures according to Example 1, and a positive active material according to comparative Example 1;
FIGS. 2a and 2 b are scanning electron microscopy (SEM) photographs illustrating a material heat-treated at a low temperature in Example 1 of the present invention;
FIGS. 3a and 3 b are SEM photographs illustrating a positive active material heat-treated at low and high temperatures according to Example 1 of the present invention;
FIGS. 4a and 4 b are SEM photographs illustrating a positive active material according to Comparative example 1;
FIG. 5a is a graph illustrating an electron probe microanalysis (EPMA) result of a positive active material according to Example 1 of the present invention;
FIG. 5b is a SEM photograph of the positive active material sample used in the EPMA;
FIG. 6 is a graph illustrating high-temperature characteristics of the positive active material according to Example 1 of the present invention, Comparative Examples 1 and Comparative Example 2 (Li1.03Mn1.97Co0.03O4); and
FIG. 7 is a graph illustrating initial charge and discharge characteristics of the positive active materials according to Example 1 and Comparative Example 1.
DETAILED DESCRIPTION OF THE INVENTION
The positive active material of the present invention is Li1+xMn2−yCoyO4−01.1<x<01 and 0<y>0.1 and has a concentration gradient of Co. That is, the positive active material of the present invention has a higher concentration of Co in a surface portion than in a central portion. The surface portion is preferably a region from an outermost surface to a depth of 10 microns.
The positive active material preparation will be now described in more detail. Cobalt salts and lithium salts are weighed in the desired ratio, the salts and a chelating agent are mixed with an alcohol, and the mixture is heated to prepare a sol or a gel type cobalt material. The cobalt salt may be cobalt hydroxide, cobalt nitrate or cobalt carbonate, and the lithium salt may be lithium carbonate, lithium nitrate or lithium hydroxide. The chelating agent may be oxalic acid, citric acid or glycine, and the alcohol may be ethanol or methanol. The cobalt salts, lithium salts and alcohols are not limited to the above compounds.
The sol or gel type cobalt material is mixed with LiMn2O4. The mixing ratio of the cobalt material and LiMn2O4 is from 1:99 to 5:95 wt %. If the amount of the cobalt material is more than 5 wt %, the amount of Co doped into LiMn2O4 is too large and it may act as an impurity. But, if the amount of the cobalt material is less than 1 wt %, the desired effect of doping Co in the LiMn2O4 is not induced.
It is preferable to use LiMn2O4 having a spinel phase. LiMn2O4 may be produced by mixing manganese salts with lithium salts in the desired ratio and sintering the mixture at a temperature ranging from about 750 to 800° C. Alternatively, LiMn2O4 may be commercially purchased. The manganese salts may be manganese acetate or manganese dioxide, and the lithium salts may be lithium carbonate, lithium nitrate or lithium hydroxide. The manganese salts and lithium salts are not limited to the above compounds.
The mixture of the cobalt material and manganese compound is heat-treated at a temperature ranging from 550 to 850° C. The heat-treatment temperature preferably ranges from 700 to 850° C. because the crystallinity of LiCoO2 is increased. Prior to the heat-treatment step, a pre-heat-treatment step may be performed at a temperature ranging from 100 to 300° C. In the heat-treatment step, LiCoO2 reacts with LiMn2O4 to generate Li1+xMn2−yCoyO4 wherein 0.1<x<0.1 and 0<y<0.1. The reaction occurs more actively in the surface portion than in the central portion, and thus the Co content in the surface portion of LiMn2O4 is higher than in the central portion thereof. The surface portion, as indicated, refers to a region from an outermost surface to a depth of 10 microns. The ratio of the concentration of Co in the central portion to that in the surface portion ranges from 1:1.05 to 1:1.3.
Electrolytes of rechargeable lithium batteries are generally non-aqueous, but a trace of water may be present in the electrolytes. Water reacts with lithium salts such as LiPF6 in the electrolyte to generate strong acids such as HF. The generated HF attacks Mn present at the surface of the manganese-based positive active material, and Mn is eluted into the electrolyte such that the active material disintegrates. As a result, the cycle life characteristics, particularly the high-temperature cycle life characteristics, are extremely deteriorated. In the present invention, Co, which is abundant in the surface of LiMn2O4, protects Mn against attack by HF.
The positive active material is used in rechargeable lithium batteries. In rechargeable lithium batteries, a negative electrode is produced with a carbonaceous active material such as graphite or carbon, from or into which lithium ions are deintercalated or intercalated. A non-aqueous liquid electrolyte or a polymer electrolyte may be used. For separators, polymer films known in the related arts may be used.
The following examples further illustrate the present invention.
EXAMPLE 1
Lithium acetate and cobalt acetate in the molar ratio of 1:2 were added to 50 ml of methanol, and the mixture was uniformly shaken using a magnetic bar. 2 g of citric acid were then added to the mixture, and the resulting mixture was heated at 50° C. until a sticky gel was obtained. LiMn2O4 powder was added to the gel and uniformly mixed. Thereafter, the mixture obtained was pre-heat-treated at 150° C. for 3 hours, and the pre-heat-treated material was again heat-treated at 800° C. for 12 hours to produce a positive active material for a rechargeable lithium battery.
Comparative Example 1
Li2CO3 was uniformly mixed with MnO2 and the mixture was sintered at 790° C. for 24 hours. The sintered material was cooled to room temperature to produce LiMn2O4.
Comparative Example 2
Li2CO3, MnO2 and Co(OH)2 were mixed, and the mixture was sintered at 790° C. for 24 hours to produce Li1.03Mn1.97CO0.03O4.
The XRD of the material pre-heat-treated at 150° C. and the positive active material heat-treated at 800° C. according to Example 1 were measured, and the results are shown in FIG. 1. The XRD result of the positive active material according to Comparative Example 1 is also shown in FIG. 1. As shown in FIG. 1, the material pre-heat-treated at 150° C. (B in FIG. 1) and the positive active material heat-treated at 800° C. for 12 hours (C in FIG. 1) exhibit no LiCoO2 phase, like the positive active material according to Comparative Example 1 (A in FIG. 1). The results indicate that a very thin layer of LiCoO2 is coated on LiMn2O4.
SEM photographs of the pre-heat-treated material and the heat-treated active material according to Example 1 are presented in FIGS. 2a and b, and FIGS. 3a and b respectively. FIGS. 4a and b show the SEM photographs of the active material according to Comparative Example 1. FIGS. 2b, 3 b and 4 b are the SEM photographs of FIGS. 2a, 3 a, and 4 a, respectively, enlarged 10 times. The surface of the material heat-treated at 150° C. (FIGS. 2a and b) is different from that of LiMn2O4 (FIGS. 4a and b). Whereas, the surface of the positive active material which was again heat-treated at 800° C. is similar to that of LiMn2O4. That is, the material heat-treated at the low temperature has the LiCoO2 coating layer such that it has a smooth surface, which is different from that of LiMn2O4, but the material heat-treated again has no LiCoO2 coating layer or octahedral type spinel, similar to LiMn2O4. The results show that LiCoO2 reacts with LiMn2O4 at high temperatures to generate Li1+xMn2−yCoyO4. In fact, elemental analysis results show that the powder heat-treated at 800° C. was Li1.03Mn1.97Co0.03O4.
The reaction occurred more actively at the surface such that the concentration of Co in the surface portion is higher than that in the central portion. For determining the concentration of Co in the surface portion in comparison to that in the central portion, electron probe microanalysis (EPMA) ofthe active material according to Example 1 was performed. The results are presented in FIG. 5a. In FIG. 5a, the x axis (distance within a particle) indicates the line shown as the particle diameter in FIG. 5b. FIG. 5b shows a SEM photograph of the positive active material sample used in the EPMA. As shown in FIG. 5a, the Co content in the active material according to Example 1 is highest at the outermost surface portion and is higher than the central portion from the outermost surface to a depth of 10 microns.
It is believed that the high concentration of Co in the surface portion prevents the elution of Mn and stabilizes the structure of the active material. This belief is supported by the high-temperature (55° C.) cycle life characteristics results shown in FIG. 6. FIG. 6 shows the high-temperature (55° C.) cycle life characteristics of the half-cell using the positive active material according to Example 1, Comparative Example 1 and Comparative Example 2 (Synthesized Li1.03Mn1.97Co0.03O4). In the half-cell, metallic lithium was used as the reference electrode, and polyvinylidene fluoride was used as the binder. Carbon black was used as the conductive agent, and N-methyl pyrrolidone was used as the solvent. The separator was obtained from Celgard Co., and the electrolyte used was LiPF6 in ethylene carbonate and dimethyl carbonate. As shown in FIG. 6, the active material according to Example 1 exhibited excellent high-temperature cycle life characteristics.
FIG. 7 shows the initial charge and discharge capacity of the half-cells. The cell according to Example 1 exhibited a smaller irreversible capacity than that of Comparative Example 1.
As described above, the positive active material of the present invention has a surface coated with LiCoO2, which stops the elution of Mn, so the positive active material has cycle life characteristics that are improved by at least 20%, compared with LiMn2O4.
While the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that various modifications and substitutions can be made thereto without departing from the spirit and scope of the present invention as set forth in the appended claims.

Claims (14)

What is claimed is:
1. A positive active material for a rechargeable lithium battery represented by the formula Li1+xMn2−yCoyO4, wherein −0.1≦x≦0.1 and 0<y<0.1, having a concentration of Co in a surface portion higher than that in a central portion, with the surface portion being a region from an outermost surface of the positive active material to a depth of 10 microns, wherein the ratio of the concentration of Co in the central portion to that in the surface portion ranges from 1:1.05 to 1:1.30.
2. A method of preparing a positive active material for a rechargeable lithium battery comprising the steps of:
obtaining a sol or gel-cobalt material by mixing lithium salts, cobalt salts, an alcohol and chelating agents and heating the mixture;
mixing the sol or gel-cobalt material with LiMn2O4; and
heat-treating the mixture,
wherein the positive active material is Li1+xMn2−yCoyO4 where −0.1≦x≦0.1 and 0<y<0.1 and has a concentration of Co in a surface portion higher than that in a central portion, the surface portion being a region from an outermost surface of the positive active material to a depth of 10 microns.
3. The method of claim 2 wherein the ratio of the cobalt material to LiMn2O4 ranges from 1:99 to 5:95 (1 to 5:99 to 95) wt %.
4. The method of claim 2 wherein the mixture is heat-treated at a temperature ranging from 550 to 850° C.
5. The method of claim 2 wherein the cobalt material is LiCoO2.
6. The method of claim 2 wherein the cobalt salt is selected from the group consisting of cobalt hydroxide, cobalt nitrate and cobalt carbonate.
7. The method of claim 2 wherein the lithium salt is selected from the group consisting of lithium carbonate, lithium nitrate and lithium hydroxide.
8. The method of claim 2 wherein the chelating agent is selected from the group consisting of oxalic acid, citric acid and glycine.
9. The method of claim 2 wherein the alcohol is selected from the group consisting of ethanol and methanol.
10. The method of claim 2 wherein the LiMn2O4 has a spinal phase.
11. The method of claim 2 wherein the mixture of the sol or gel cobalt material and LiMn2O4 is heat treated at a temperature ranging from 550 to 850° C.
12. The method of claim 11 wherein the mixture of the sol or gel cobalt material and LiMn2O4 is heat treated at a temperature ranging from 700 to 850° C.
13. The method of claim 2 further comprising a pre-heat-treatment step.
14. The method of claim 13, wherein the pre-heat-treatment step is performed at a temperature ranging from 100 to 300° C.
US09/669,775 1999-11-17 2000-09-22 Positive active material for rechargeable lithium battery and method of preparing same Expired - Lifetime US6274273B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
KR1019990051149A KR100315227B1 (en) 1999-11-17 1999-11-17 Positive active material for lithium secondary battery a method of preapring the same
KR99-51149 1999-11-17

Publications (1)

Publication Number Publication Date
US6274273B1 true US6274273B1 (en) 2001-08-14

Family

ID=19620555

Family Applications (1)

Application Number Title Priority Date Filing Date
US09/669,775 Expired - Lifetime US6274273B1 (en) 1999-11-17 2000-09-22 Positive active material for rechargeable lithium battery and method of preparing same

Country Status (3)

Country Link
US (1) US6274273B1 (en)
JP (1) JP4068796B2 (en)
KR (1) KR100315227B1 (en)

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6506524B1 (en) * 1996-10-03 2003-01-14 National Research Council Of Canada Electrolyte comprising fluoro-ethylene carbonate and propylene carbonate, for alkali metal-ion secondary battery
WO2004040677A1 (en) 2002-10-31 2004-05-13 Lg Chem, Ltd. Lithium transition metal oxide with gradient of metal composition
US20040121234A1 (en) * 2002-12-23 2004-06-24 3M Innovative Properties Company Cathode composition for rechargeable lithium battery
WO2003009407A3 (en) * 2001-07-14 2004-10-28 Univ St Andrews Managanese oxide material for electrochemical cells
US20050112054A1 (en) * 2003-11-26 2005-05-26 3M Innovative Properties Company Solid state synthesis of lithium ion battery cathode material
US20060062721A1 (en) * 2004-09-22 2006-03-23 Ming-Tseh Tsay Process of preparing lithium cobalite powders
US20060147798A1 (en) * 2001-04-27 2006-07-06 3M Innovative Properties Company Cathode compositions for lithium-ion batteries
US20060159994A1 (en) * 2001-08-07 2006-07-20 Dahn Jeffrey R Cathode compositions for lithium ion batteries
EP1716609A1 (en) * 2003-12-31 2006-11-02 LG Chem, Ltd. Electrode active material powder with size dependent composition and method to prepare the same
US20070068878A1 (en) * 2000-01-19 2007-03-29 Stever R R Stormwater treatment apparatus and method
US20090068561A1 (en) * 2006-03-30 2009-03-12 Yang-Kook Sun Positive active material for lithium battery, method of preparing the same, and lithium battery including the same
US20120288617A1 (en) * 2011-05-12 2012-11-15 Applied Materials, Inc. Precursor formulation for battery active materials synthesis
WO2014180743A1 (en) * 2013-05-08 2014-11-13 Basf Se Spherical particles, production and use thereof
US20150372293A1 (en) * 2013-02-01 2015-12-24 Tronox Llc Improved lithium manganese oxide compositions
US20160093876A1 (en) * 2014-09-26 2016-03-31 United States Government, As Represented By The Secretary Of The Army LixMn2O4-y(Clz) SPINEL CATHODE MATERIAL, METHOD OF PREPARING THE SAME, AND RECHARGEABLE LITHIUM AND LI-ION ELECTROCHEMICAL SYSTEMS CONTAINING THE SAME
CN109301242A (en) * 2018-09-19 2019-02-01 河南工学院 A kind of lithium ion cell positive benefit lithium material Li5FeO4Preparation method and application
EP3509141A4 (en) * 2016-08-30 2019-09-25 Shandong Yuhuang New Energy Technology Co., Ltd. High-quality, lithium-rich and manganese-based positive electrode material for lithium ion battery, and method for synthesizing same
CN117525386A (en) * 2024-01-08 2024-02-06 宁波容百新能源科技股份有限公司 High-nickel positive electrode material, and preparation method and application thereof

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1855587B (en) * 2005-04-28 2010-05-05 比亚迪股份有限公司 Battery anode preparation method and preparation method of lithium ion batteries using the battery anode
CN101405899B (en) 2006-03-20 2012-04-04 株式会社Lg化学 Cathode materials for lithium battery having higher performance
CN104979547B (en) 2006-03-20 2018-02-06 株式会社Lg化学 Lithium and cobalt oxides of stoichiometry and preparation method thereof

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5783332A (en) * 1995-04-26 1998-07-21 Japan Storage Battery Co., Ltd. Positive electrode active material for lithium battery and a method for manufacturing the same
US6103422A (en) * 1995-12-26 2000-08-15 Kao Corporation Cathode active material and nonaqueous secondary battery containing the same

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5783332A (en) * 1995-04-26 1998-07-21 Japan Storage Battery Co., Ltd. Positive electrode active material for lithium battery and a method for manufacturing the same
US6103422A (en) * 1995-12-26 2000-08-15 Kao Corporation Cathode active material and nonaqueous secondary battery containing the same

Cited By (43)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6506524B1 (en) * 1996-10-03 2003-01-14 National Research Council Of Canada Electrolyte comprising fluoro-ethylene carbonate and propylene carbonate, for alkali metal-ion secondary battery
US20070068878A1 (en) * 2000-01-19 2007-03-29 Stever R R Stormwater treatment apparatus and method
US20060147798A1 (en) * 2001-04-27 2006-07-06 3M Innovative Properties Company Cathode compositions for lithium-ion batteries
US8241791B2 (en) 2001-04-27 2012-08-14 3M Innovative Properties Company Cathode compositions for lithium-ion batteries
US8685565B2 (en) 2001-04-27 2014-04-01 3M Innovative Properties Company Cathode compositions for lithium-ion batteries
WO2003009407A3 (en) * 2001-07-14 2004-10-28 Univ St Andrews Managanese oxide material for electrochemical cells
US20060159994A1 (en) * 2001-08-07 2006-07-20 Dahn Jeffrey R Cathode compositions for lithium ion batteries
US7368071B2 (en) 2001-08-07 2008-05-06 3M Innovative Properties Company Cathode compositions for lithium ion batteries
US20060105239A1 (en) * 2002-10-31 2006-05-18 Paulsen Jens M Lithium transition metal oxide with gradient of metal composition
US7695649B2 (en) 2002-10-31 2010-04-13 Lg Chem, Ltd. Lithium transition metal oxide with gradient of metal composition
EP3121882A1 (en) 2002-10-31 2017-01-25 LG Chem, Ltd. Lithium transition metal oxide with gradient of metal composition
WO2004040677A1 (en) 2002-10-31 2004-05-13 Lg Chem, Ltd. Lithium transition metal oxide with gradient of metal composition
US20040121234A1 (en) * 2002-12-23 2004-06-24 3M Innovative Properties Company Cathode composition for rechargeable lithium battery
US20050112054A1 (en) * 2003-11-26 2005-05-26 3M Innovative Properties Company Solid state synthesis of lithium ion battery cathode material
US7211237B2 (en) 2003-11-26 2007-05-01 3M Innovative Properties Company Solid state synthesis of lithium ion battery cathode material
US20070202407A1 (en) * 2003-11-26 2007-08-30 3M Innovative Properties Company Solid state synthesis of lithium ion battery cathode material
US7488465B2 (en) 2003-11-26 2009-02-10 3M Innovative Properties Company Solid state synthesis of lithium ion battery cathode material
US20100264363A1 (en) * 2003-12-31 2010-10-21 Jens Martin Paulsen Electrode active material powder with size dependent composition and method to prepare the same
US7771877B2 (en) 2003-12-31 2010-08-10 Lg Chem, Ltd. Electrode active material powder with size dependent composition and method to prepare the same
US8012626B2 (en) 2003-12-31 2011-09-06 Lg Chem, Ltd. Electrode active material powder with size dependent composition and method to prepare the same
US20070122705A1 (en) * 2003-12-31 2007-05-31 Lg Chem. Ltd. Electrode active material powder with size dependent composition and method to prepare the same
EP1716609A4 (en) * 2003-12-31 2009-07-22 Lg Chemical Ltd Electrode active material powder with size dependent composition and method to prepare the same
EP1716609A1 (en) * 2003-12-31 2006-11-02 LG Chem, Ltd. Electrode active material powder with size dependent composition and method to prepare the same
EP3432392A1 (en) * 2003-12-31 2019-01-23 LG Chem, Ltd. Electrode active material powder with size dependent composition and method to prepare the same
US20060062721A1 (en) * 2004-09-22 2006-03-23 Ming-Tseh Tsay Process of preparing lithium cobalite powders
US20090068561A1 (en) * 2006-03-30 2009-03-12 Yang-Kook Sun Positive active material for lithium battery, method of preparing the same, and lithium battery including the same
US10367197B2 (en) 2006-03-30 2019-07-30 Industry-University Cooperation Foundation Hanyang University Positive active material composition for lithium battery, method of preparing the same, and lithium battery including the same
US8865348B2 (en) 2006-03-30 2014-10-21 Industry-University Cooperation Foundation, Hanyang University Positive active material comprising a continuous concentration gradient of a metal composition for lithium battery, method of preparing the same, and lithium battery including the same
CN103518276A (en) * 2011-05-12 2014-01-15 应用材料公司 Precursor formulation for battery active materials synthesis
US20120288617A1 (en) * 2011-05-12 2012-11-15 Applied Materials, Inc. Precursor formulation for battery active materials synthesis
US9112225B2 (en) * 2011-05-12 2015-08-18 Applied Materials, Inc. Precursor formulation for battery active materials synthesis
US20150372293A1 (en) * 2013-02-01 2015-12-24 Tronox Llc Improved lithium manganese oxide compositions
US10522822B2 (en) * 2013-02-01 2019-12-31 Emd Acquisition Llc Lithium manganese oxide compositions
CN105377765A (en) * 2013-05-08 2016-03-02 巴斯夫欧洲公司 Spherical particles, production and use thereof
CN105377765B (en) * 2013-05-08 2018-01-26 巴斯夫欧洲公司 Spheric granules, it is prepared and purposes
US10069144B2 (en) 2013-05-08 2018-09-04 Basf Se Spherical particles, production and use thereof
WO2014180743A1 (en) * 2013-05-08 2014-11-13 Basf Se Spherical particles, production and use thereof
US20160093876A1 (en) * 2014-09-26 2016-03-31 United States Government, As Represented By The Secretary Of The Army LixMn2O4-y(Clz) SPINEL CATHODE MATERIAL, METHOD OF PREPARING THE SAME, AND RECHARGEABLE LITHIUM AND LI-ION ELECTROCHEMICAL SYSTEMS CONTAINING THE SAME
US9979011B2 (en) * 2014-09-26 2018-05-22 The United States Of America As Represented By The Secretary Of The Army LixMn2O4-y(C1z) spinal cathode material, method of preparing the same, and rechargeable lithium and li-ion electrochemical systems containing the same
EP3509141A4 (en) * 2016-08-30 2019-09-25 Shandong Yuhuang New Energy Technology Co., Ltd. High-quality, lithium-rich and manganese-based positive electrode material for lithium ion battery, and method for synthesizing same
CN109301242A (en) * 2018-09-19 2019-02-01 河南工学院 A kind of lithium ion cell positive benefit lithium material Li5FeO4Preparation method and application
CN117525386A (en) * 2024-01-08 2024-02-06 宁波容百新能源科技股份有限公司 High-nickel positive electrode material, and preparation method and application thereof
CN117525386B (en) * 2024-01-08 2024-05-14 宁波容百新能源科技股份有限公司 High-nickel positive electrode material, and preparation method and application thereof

Also Published As

Publication number Publication date
JP4068796B2 (en) 2008-03-26
KR100315227B1 (en) 2001-11-26
JP2001143710A (en) 2001-05-25
KR20010047099A (en) 2001-06-15

Similar Documents

Publication Publication Date Title
US6274273B1 (en) Positive active material for rechargeable lithium battery and method of preparing same
KR100797099B1 (en) Positive active material for a lithium secondary battery, method of preparing thereof, and lithium secondary battery comprising the same
JP3195175B2 (en) Non-aqueous solvent secondary battery
EP1909345B1 (en) Cathode active material for a lithium battery
US6007947A (en) Mixed lithium manganese oxide and lithium nickel cobalt oxide positive electrodes
EP2096692B1 (en) Cathode active material, and cathode and lithium battery including the same
US6582852B1 (en) Metal oxide containing multiple dopants and method of preparing same
KR100815583B1 (en) Positive active material for a lithium secondary battery, method of preparing thereof, and lithium secondary battery comprising the same
US7927506B2 (en) Cathode active material and lithium battery using the same
JP2023523667A (en) Positive electrode active material, manufacturing method thereof, and lithium secondary battery including positive electrode containing the same
KR100420034B1 (en) A method of preparing a positive active material for a lithium secondary battery
JP3141858B2 (en) Lithium transition metal halide oxide, method for producing the same and use thereof
EP1207574A1 (en) Positive active material for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery comprising same
JP4235702B2 (en) Positive electrode active material, manufacturing method thereof, and nonaqueous electrolyte secondary battery using the same
US6972134B2 (en) Method of preparing positive active material for rechargeable lithium batteries
JP2002134110A (en) Method of producing positive electrode active material and method of producing nonaqueous electrolyte battery
JP2974213B1 (en) Positive electrode active material for lithium secondary battery, method for producing the same and use thereof
JPH09293508A (en) Positive electrode material for lithium secondary battery, its manufacture and nonaqueous electrolyte secondary battery using it
JP2000348722A (en) Nonaqueous electrolyte battery
KR100555972B1 (en) Cathode active material and lithium secondary battery employing the same
KR101602419B1 (en) Cathode active material cathode comprising the same and lithium battery using the cathode
KR101588362B1 (en) Cathode active material having core-shell structure and manufacturing method therof
JP2002063904A (en) Positive electrode active material and nonaqueous electrolyte battery as well as their manufacturing method
JP2002184404A (en) Positive electrode material and nonaqueous electrolyte battery
JPH10241687A (en) Nonaqueous electrolyte secondary battery

Legal Events

Date Code Title Description
AS Assignment

Owner name: SAMSUNG SDI CO., LTD., KOREA, REPUBLIC OF

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:CHO, JAE-PHIL;KIM, GEUN-BAE;PARK, YONG-CHUL;REEL/FRAME:011139/0238

Effective date: 20000825

STCF Information on status: patent grant

Free format text: PATENTED CASE

FEPP Fee payment procedure

Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

CC Certificate of correction
FPAY Fee payment

Year of fee payment: 4

FPAY Fee payment

Year of fee payment: 8

FEPP Fee payment procedure

Free format text: PAYER NUMBER DE-ASSIGNED (ORIGINAL EVENT CODE: RMPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

FPAY Fee payment

Year of fee payment: 12